Conventionally, ARQ (Auto Repeat reQuest) is known as a retransmission technique in a radio communication. Furthermore, there is also a proposal of HARQ (Hybrid Auto Repeat reQuest) which combines turbo coding having high error correction performance and ARQ. In HARQ, by using puncturing processing, it is possible to suppress decrease in data transmission efficiency caused by retransmission. Such a conventional technique using ARQ and puncturing processing is disclosed in Non-Patent Document 1 and Non-Patent Document 2.
FIG. 1 shows a configuration example of a conventional transmission apparatus using ARQ and puncturing processing. Transmission apparatus 20 inputs transmission digital signal 1 to CRC (Cyclic Redundancy Check) encoder 2. CRC encoder 2 transmits transmission digital signal 3 after CRC encoding to convolution code encoder 4. Convolution code encoder 4 performs convolution encoding processing on transmission digital signal 3 after CRC encoding and transmits transmission digital signal 5 after convolution encoding to puncturing section 6.
Puncturing section 6 performs puncturing on transmission digital signal 5 after convolution encoding and transmits transmission digital signal 7 after puncturing to selection section 12 and also transmits redundant information 8 generated upon encoding to storage section 9. Here, when, for example, convolution code encoder 4 performs encoding at a coding rate of 1/2, puncturing section 6 forms transmission digital signal 7 after puncturing, for example, at a coding rate of 3/4.
Redundant information 8 stored in storage section 9 is discarded when an ACK (acknowledgement) signal is transmitted as ACK/NACK signal 11 from a communicating party, and transmitted to selection section 12 as a retransmission signal when a NACK (negative-acknowledgement) signal is transmitted.
Selection section 12 selects and outputs transmission digital signal 7 after puncturing when an ACK signal is inputted, and, on the other hand, selects and outputs redundant information 10 stored in storage section 9 when a NACK signal is inputted. That is, selection section 12 selects redundant information 10 as a retransmission signal only when there is a retransmission request.
Modulation section 14 performs modulation such as QPSK and 16 QAM on transmission digital signal 13 selected by selection section 12 and transmits modulated signal 15 obtained in this way to radio section (RF section) 16. RF section 16 performs predetermined radio processing such as frequency conversion on modulated signal 15 and transmits transmission signal 17 obtained in this way to antenna 18.    Non-Patent Document 1: “Rate-compatible punctured convolutional codes and their applications”, IEEE Transactions on Communications, pp. 389-400, vol. 36, no. 4, April 1988.    Non-Patent Document 2: “Generalized Type II Hybrid ARQ scheme using punctured convolutional coding” IEEE Transactions on Communications, pp. 1938-1946, vol. 38, no. 11, November 1990.